I. Field of the Invention
The present invention relates to intravascular catheters, and more particularly to a diagnostic catheter having a relatively small outside diameter for its relatively large diameter internal lumen and which possesses excellent pushability and torqueability characteristics.
II. Discussion of the Prior Art
In evaluating the progress of coronary artery disease in patients, angiography procedures are used to view the patency of selected blood vessels. In carrying out this procedure, a diagnostic catheter having a desired distal end curvature configuration is introduced into the femoral artery using the Seldinger technique and advanced over a guide wire through the vascular system of the patient until the distal end of the catheter is steered into the particular coronary artery to be examined. With smaller patients, a brachial approach may be used.
In that the path taken by the diagnostic catheter is quite tortuous, it is essential to a good diagnostic catheter that it can be steered by torquing its proximal hub and that the torque be transmitted to the distal end in a smooth, controllable fashion. Moreover, the catheter must have sufficient strength in the longitudinal direction so as not to kink or fold as it is advanced through the vascular system. It must also possess a lubricous core lumen to facilitate passage of a guidewire or possibly another catheter therethrough.
It is also a desirable feature of a diagnostic catheter that it possess a relatively large lumen to allow fluids, such as radiopaque contrast fluid to be injected therethrough and out the distal end so that the area of the vascular system under investigation can be viewed fluoroscopically.
The desirable properties of a catheter having a relatively small O.D. and a relatively large I.D. dictates a fairly thin wall. To maintain the desired torqueability and pushability characteristics of a thin wall catheter calls for considerable ingenuity in the formulation of the materials employed and the constructional techniques utilized.
The Jang et al. U.S. Pat. No. 4,898,591 describes a diagnostic catheter having a tubular body formed from inner and outer tubular layers, there being a strengthening braid interposed between the inner and outer layers. Each of the inner and outer layers is formed from a blend of a nylon and an ester-linked polyether-polyamide copolymer.
The present invention is deemed to be an advance over the prior art as represented by the Jang et al. patent in that it provides a diagnostic catheter having a minimal O.D. and a maximal I.D. while still maintaining the necessary torqueability and pushability characteristics. Using the method and the constituents for the various layers set forth herein, it has been possible to design a diagnostic catheter having, for example, a 4 Fr O.D. but with an internal lumen that is as large as the internal lumen of a 5 Fr catheter that is currently commercially available. Similarly, a 6 Fr catheter made in accordance with the present invention possesses an internal lumen that is about equal to that of a commercially-available 7 Fr catheter.